The Cigarra Collection of U.S. coins missing Mint marks offered at auction through April 5 by GreatCollections Coin Auctions includes the Proof 1968 No S Roosevelt dime and Proof 1990 No S Lincoln cent.

Also included in the collection of the anonymous East Coast collector is a 1970 No S Roosevelt dime, 1971 No S Jefferson 5-cent coin, and 1983 No S Roosevelt dime, all in Proof. All of the error coins offered would have originated from annual Proof sets from the respective years.

Missing from the Cigarra Collection is the Proof 1975 No S Roosevelt dime, of which just two examples are known, and the Uncirculated 1982 No P Roosevelt dime struck without the P Mint mark of the Philadelphia Mint.

The cause of the missing Mint mark errors is the same — the dies used for striking each coin did not have the appropriate S Mint mark from the San Francisco Assay Office added. During this time frame, the dies for the coins would have been prepared in the die shop at the Philadelphia Mint, including having the S Mint mark applied, before being shipped to the San Francisco facility. In each case, either a Mint mark was not added in error or a die intended to be used for circulation production at the Philadelphia Mint was shipped in error to the San Francisco Assay Office, where it was given Proof surfaces.

Of the collectible variants, the Proof 1968 No S Roosevelt dime is considered the rarest. Based on the surviving population of fewer than two dozen coins, numismatic researchers believe San Francisco Mint production employees discovered the mistake early in the production.

Proof 1990 No S Roosevelt dimes were discovered in both the annual Proof sets and Prestige Proof sets of 1990, with the Prestige set containing a Proof 1990-P Eisenhower Centennial commemorative silver dollar.

U.S. Mint officials acknowledged that approximately 3,700 of the 1990 No S Lincoln cents were struck, with 145 examples destroyed before they were shipped from the Mint. Researchers believe fewer than 3,555 Proof and Prestige Proof sets actually left the San Francisco Mint, since fewer than 250 examples have been reported extant thus far.

The 1970 No S Roosevelt dime was first reported by collectors on Jan. 6, 1971. Two months later, U.S. Mint officials admitted the No S dime population at 2,200 coins, having been struck with the same pair of dies. A die scratch beneath the right upright of the N in UNITED is a diagnostic.

The 1971 No S Jefferson 5 cent coin was included in a reported 1,655 1971 Proof sets.

The 1983 No S Roosevelt dime, like the 1970 No S dime, are collectible and available to collectors seeking examples for their collections.

Mint marks were added to all U.S. coins in 1980 except for Lincoln cents struck at the Philadelphia Mint. Mint officials announced in 1984 that the following year, all Mint marks would be placed on Proof coinage on the master die instead of the working die.

Beginning in 1990, the Mint marks were placed on the master die for the cents and 5-cent coins, with the dimes, quarter dollars and half dollars undergoing the same transformation in 1991.